1. Field of the Invention
The present invention relates to an acoustic signal processing apparatus which controls an acoustic signal to make the frequency response of tone volume of the acoustic signal appropriate to a set tone volume.
2. Description of the Related Art
It has been known that the human auditory sense has a characteristic that the perception of loudness varies depending on frequency band. For example, the loudness perception decreases in low frequencies and high frequencies. Because of this characteristic, when the whole volume is reduced on an acoustic apparatus, tones based on low frequencies and high frequencies of acoustic signals are hard to be heard, losing balance of the whole loudness perception. In order to compensate such a human auditory sense, conventional acoustic apparatuses are equipped with a loudness capability for emphasizing low frequencies and high frequencies of acoustic signals when the set tone volume is reduced, as described in Japanese Unexamined Patent Publication No. 64-51706, for example. The loudness capability keeps balance of the whole loudness perception by increasing the gains of low frequencies and high frequencies when the whole tone volume is reduced.